Horizontal cells of the cat retina were isolated by enzymatic dissociation. Two types of horizontal cells were identified: the axonless (A-type) horizontal cell having four to six thick, long (approximately 100 microns) dendrites, and the short-axon (B-type) horizontal cell having many (> 5) fine, short (approximately 30 microns) dendrites. 2. Membrane properties of isolated horizontal cells were analyzed under current-clamp and voltage-clamp conditions. In the A-type cell, the average resting potential was -55 mV and the mean membrane capacitance was 110 pF, whereas values in the B-type cell were -58 mV and 40 pF, respectively. The A-type cell showed long-lasting Ca spikes, but B-type cells had no Ca spikes. 3. Five types of voltage-dependent ionic currents were recorded: a sodium current (INa), a calcium current (ICa), and three types of potassium currents. Potassium currents consisted of potassium current through the inward rectifier (Ianomal), transient outward potassium current (IA), and potassium current through the delayed rectifier (IK(v)). INa was recorded only from A-type cells. Other currents were recorded from both types of cells. 4. INa activated when cells were depolarized from a holding potential (Vh) of -95 mV, and it was maximal at -25 mV. This current was blocked by tetrodotoxin. Approximately half of the A-type cells had INa, but no B-type cell had this current. 5. L-type ICa, an inward-going sustained current, was activated with depolarization more positive than -25 mV. Current amplitude reached a maximal value near 15 mV and became smaller with further depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)
摘要
通过酶解分离出猫视网膜的水平细胞。鉴定出两种类型的水平细胞：无轴突（A 型）水平细胞，具有四到六个粗且长（约 100 微米）的树突；短轴突（B 型）水平细胞，具有许多（>5）细且短（约 30 微米）的树突。2. 在电流钳和电压钳条件下分析分离出的水平细胞的膜特性。在 A 型细胞中，平均静息电位为 -55 mV，平均膜电容为 110 pF，而 B 型细胞中的值分别为 -58 mV 和 40 pF。A 型细胞表现出持续时间长的钙尖峰，但 B 型细胞没有钙尖峰。3. 记录到五种电压依赖性离子电流：钠电流（INa）、钙电流（ICa）和三种钾电流。钾电流包括通过内向整流器的钾电流（Ianomal）、瞬时外向钾电流（IA）和通过延迟整流器的钾电流（IK(v)）。仅从 A 型细胞中记录到 INa。两种类型的细胞都记录到了其他电流。4. 当细胞从 -95 mV 的钳制电位（Vh）去极化时，INa 被激活，在 -25 mV 时达到最大值。该电流被河豚毒素阻断。大约一半的 A 型细胞有 INa，但没有 B 型细胞有这种电流。5. L 型 ICa 是一种内向持续电流，在去极化超过 -25 mV 时被激活。电流幅度在 15 mV 附近达到最大值，并随着进一步去极化而减小。（摘要截断于 250 字）
